Design Of Casting Process For BOSS Part In Excavator Large Arm

BOSS,a part connecting the big arm and the frame,is one of the key components of the excavator.Compared with other production modes,such as forging and welding,casting has the advantages of low cost,little cracking probability and so on.Therefore,our factory decided to cast molding the BOSS.But,if adopting the conventional casting process,there will be a possibility of a crack in the BOSS which the original manufacturer encountered the problem,and sands in the axle hole be not easy to clean.So,the conventional casting process cannot be directly used.The process must be improved or adopted other new casting technology.Normally,before the new casting process is put into practice,it has to be tested several times.Long time and high material cost is contrary to the cost saving and the time reducing required by our factory.To solve this contradiction,based on PROCAST software,the paper analyzed casting process of the BOSS,which focused on the causes of thermal cracks in the conventional casting process and the influence on casting quality after changing core material,and solved the problem of the casting thermal crack.Combination with physical tryout,the paper also solved the problem hard to clean sands in the casting axle hole.The results show that:1.The reason for crack initiation in the original production is that the large size of the outer cold iron is placed at the bottom of the casting.The combination of factors,such as the friction resistances on casting/cold-iron interface,the interaction forces caused by solidified and unsolidified sections in the wall thickness transitional region,the mechanical constraining forces coming from sand core and sand mold,and so on,lead to the risk increase of hot tearing when the casting cooling to near the solidus temperature.2.As the hot crack trend and the casting quality under different process were compared in PROCAST,the external cold iron structure and layout don't be considered in physical tryout,so as to save the tryout time and material cost.3.The sands in BOSS bore are not easy removed by the conventional tools,so it is more favorable to obtain the inner cavity of non-sticky sand by using limestone sand core instead of silica sand core.But,it is necessary to pay more attention to mold venting.4.The technology plan for BOSS part confirmed finally in this paper is gravity casting,Silica-sand cavity and limestone-sand core,no external cold iron,pouring temperature 1565? and time 25 sec.